Prismatic battery module and method for manufacturing the same

ABSTRACT

A prismatic battery module includes a prismatic battery case having a plurality of prismatic cell cases connected to one another through separation walls, a planar electroconductive connector forming part of the separation wall between the cell cases, an electrode plate group arranged in each cell case, and an electrolyte placed in each cell case. Lead portions of positive electrode plates and negative electrode plates of the electrode plate group are directly connected to the electroconductive connector. The prismatic battery module requires fewer connection points and provides shorter electrical communication paths, thereby reducing internal resistance.

CROSS REFERENCES TO RELATED APPLICATION

This application is a continuation of prior U.S. application Ser. No.09/996,908, filed Nov. 30, 2001, which is herein expressly incorporatedby reference in its entirety.

The present disclosure relates to subject matter contained in priorityJapanese Patent Application Nos. 2000-364827 and 2001-243421, filed onNov. 30, 2000 and Aug. 10, 2001 respectively, the contents of which isherein expressly incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a prismatic battery module and a methodfor manufacturing the same. More particularly, the invention relates toa prismatic battery module which is made by connecting a plurality ofcells together and designed to reduce an internal resistance, and amethod for manufacturing the same.

2. Description of Related Art

A conventional rechargeable battery module made by connecting aplurality of cells together, each having an individual cell case, has aproblem that the connection path between the cells is long and thenumber of connection points in the battery module is large, therebyincreasing the component resistance leading to the increase of internalresistance thereof.

In consideration of the aforementioned conventional problem, theinventors of this invention have proposed a prismatic battery module 100including a plurality of cells 2 as shown in FIGS. 32 and 33. Referencenumeral 3 denotes a prismatic battery case constructed in such a mannerthat a plurality of prismatic cell cases 4 of cells 2, each cell casehaving short lateral walls and long lateral walls, are integrallyconnected together in series, and each pair of cell cases shares shortlateral walls thereof as a separation wall 5, and further, an upperopening of each of the cell cases is closed by a unitary lid 6. In theupper portions of outer short lateral walls of the outermost cell casesand the separation wall 5 between the adjacent cell cases 4 are formedconnection holes 7. Within each of the cell cases 4, an electrode plategroup 8 constructed by alternately stacking rectangular positive andnegative electrode plates interposing a separator therebetween isaccommodated together with an electrolyte. The positive and the negativeelectrode plates constituting the electrode plate group 8 project fromthe electrode plate group in opposite directions to form a lead portion9 a of the positive electrode plate and a lead portion 9 b of thenegative electrode plate, respectively. To the side ends of the leadportions 9 a, 9 b are connected collector plates 10 a, 10 b,respectively, by welding or the like.

In the upper portions of the collector plates 10 a, 10 b are formedconnection projections 11 to be fitted into the connection holes 7, andthe connection projections 11 of the collector plates 10 a, 10 b aspositive and negative poles respectively are connected to each otherbetween the adjacent cell cases 4 by welding. Furthermore, in theconnection holes 7 of the outer short lateral walls of the outermostcell cases 4 are mounted connection terminals 12 as either a positive ornegative pole, and a connection projection 13 of the connection terminal12 and the connection projection 11 of either the collector plate 10 aor 10 b are connected to each other by welding. Thus, a plurality ofcells 2 accommodated in the prismatic battery case 3 are connectedtogether in series.

Additionally, in the lid 6 are provided a communication path 14 forbalancing the internal pressure between the cell cases 4, a safety vent(not shown) for discharging the pressure when the internal pressure ofthe cell case 4 exceeds a predetermined value and a sensor fixing hole15 for fixing a temperature sensor thereto to detect the temperature ofthe cell 2.

According to the above-described construction of battery, since theelectrical communication path from the positive and negative electrodeplates of the electrode plate group 8 to the respective lead portions 9a, 9 b is short and further the adjacent lead portions 9 a, 9 b of theassociated electrode plate groups are connected to each other via theassociated collector plate 10 a, 10 b within the prismatic battery case3, the connection path between the electrode plate groups is short andthe number of connection points is small, thereby allowing the prismaticbattery module to reduce the component resistance included therein andin proportion thereto, reduce the internal resistance.

However, although the prismatic battery module 100 shown in FIGS. 32 and33 is constructed so that the connection path from the positive andnegative electrode plates to the respective collector plates 10 a, 10 bvia the respective lead portions 9 a, 9 b is short, as is denoted byarrows in FIG. 34, the adjacent collector plates 10 a, 10 b of theassociated electrode plate groups are connected at one point of bothends of the connection projections 11 located at the upper portions ofthe adjacent collector plates by welding and therefore, there have beenseen problems that the entire connection path between the adjacentelectrode plate groups becomes longer and in addition, the internalresistance between the cells becomes higher since the electricalcommunication between the adjacent collector plates is performed at onlyone point. Furthermore, there have also been seen problems that thecollector plates 10 a, 10 b employed in the battery 100 increases themanufacturing cost of battery correspondingly, and further, it isnecessary to arrange the collector plates 10 a, 10 b on both sides ofthe electrode plate group 8 and to form the upper portion of thecollector plates 10 a, 10 b so as to project beyond the upper end of theelectrode plate group 8, thereby forcing enlargement of the volume ofthe cell case 4.

SUMMARY OF THE INVENTION

In consideration of the above problems seen in the conventionaltechnique, an object of the present invention is to provide a prismaticbattery module in which the internal resistance per cell is reduced, anda method for manufacturing the same.

A prismatic battery module according to the invention includes aprismatic battery case having a plurality of prismatic cell casesconnected to one another through separation walls, an electroconductiveconnector forming at least a part of the separation wall between thecell cases, an electrode plate group arranged in each cell case, and anelectrolyte accommodated in each cell case. In the prismatic batterymodule, positive electrode plates and negative electrode plates, whichtogether constitute the electrode plate group, are connected torespective electroconductive connectors arranged on both sides of thecell case. This construction requires fewer connection points andprovides shorter electrical communication paths since the positiveelectrode plates of an electrode plate group in a cell case areconnected to the negative electrode plates of an adjacent electrodeplate group in an adjacent cell case only through the electroconductiveconnector, which forms the separation wall between the cell cases. As aresult, internal resistance is reduced. Also, the prismatic batterymodule of the present invention does not require a collector plate andthus helps reduce its volume as well as its costs.

A method for manufacturing a prismatic battery module according to theinvention, includes the steps of: connecting a plurality of prismaticcell cases with each other through separation walls, at least part ofwhich is formed of an electroconductive connector, thereby form aprismatic battery case; forming an electrode plate group having leadportions of positive and negative electrode plates by projecting oneside portion of the positive electrode plates and one side portion ofthe negative electrode plates in opposite directions, respectively;placing the electrode plate group in each of the cell cases to connectthe lead portions on either side of the electrode plate group to therespective electroconductive connectors arranged on both sides of thecell case; placing an electrolyte in the cell cases; and closing anopening of each cell case with a lid.

Another method for manufacturing a prismatic battery module according tothe invention, includes the steps of: forming a prismatic battery casehaving a space, in which a plurality of cell cases are to be formed in arow; forming an electrode plate group having lead portions of positiveand negative electrode plates by projecting one side portion of thepositive electrode plates and one side portion of the negative electrodeplates in opposite directions; connecting the lead portions of thepositive and the negative electrode plates of the adjacent electrodeplate groups with each other through electroconductive connector plates;placing the plurality of electrode plate groups, which are connectedwith each other through the electroconductive connector plates, in theprismatic battery case and providing sealing between peripheral edges ofthe electroconductive connector plates and the inner surface of theprismatic battery case; placing an electrolyte in the cell cases definedby the electroconductive connector plates; and closing an opening ofeach cell case with a lid.

While novel features of the invention are set forth in the preceding,the invention, both as to organization and content, can be furtherunderstood and appreciated, along with other objects and featuresthereof, from the following detailed description and examples when takenin conjunction with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial vertical cross-sectional view of a first embodimentof a prismatic battery module of the present invention;

FIG. 2 is a perspective view showing one end of a prismatic battery caseof the first embodiment;

FIG. 3 is a partially cutaway perspective view showing a cell case ofthe first embodiment;

FIG. 4 is a descriptive view illustrating the electrical communicationpaths in accordance with the first embodiment;

FIG. 5 is a partial vertical cross-sectional view of a variation of thefirst embodiment;

FIG. 6A is a horizontal cross-sectional view showing the adjacent regionof a separation wall in accordance with a second embodiment of theprismatic battery module of the invention, and FIG. 6B is an enlargedview of the encircled part VIB in FIG. 6A;

FIG. 7A is a horizontal cross-sectional view showing the adjacent regionof a separation wall where the lead portions are welded to the connectorplate in accordance with a third embodiment of the prismatic batterymodule of the invention, and FIG. 7B is a vertical cross-sectional frontview showing the electrical communication paths of the welding current;

FIG. 8A is a horizontal cross-sectional view showing the adjacent regionof a separation wall in accordance with a fourth embodiment of theprismatic battery module of the invention, and FIG. 8B is an enlargedview showing a variation of the encircled part VIIIB in FIG. 8A;

FIG. 9 is a horizontal cross-sectional view showing the adjacent regionof a separation wall in accordance with a fifth embodiment of theprismatic battery module of the invention;

FIG. 10 is a horizontal cross-sectional view showing the adjacent regionof a separation wall in a first variation of the fifth embodiment;

FIG. 11 is a horizontal cross-sectional view showing the adjacent regionof a separation wall in a second variation of the fifth embodiment;

FIG. 12 is a horizontal cross-sectional view showing the adjacent regionof a separation wall in a third variation of the fifth embodiment;

FIG. 13 is a horizontal cross-sectional view showing the adjacent regionof a separation wall in accordance with a sixth embodiment of theprismatic battery module of the invention;

FIG. 14 is a horizontal cross-sectional view showing the adjacent regionof a separation wall in a variation of the sixth embodiment;

FIG. 15A is a partial horizontal cross-sectional view showing aconnection between a corrugated connector plate and an electrode plategroup in accordance with a seventh embodiment of the prismatic batterymodule of the invention, FIG. 15B is an enlarged schematic view showinga part of the connector plate and the electrode plate group prior toconnection, and FIG. 15C is an enlarged schematic view showing a part ofthe connector plate and the electrode plate group connected to oneanother;

FIG. 16 is a partial horizontal cross-sectional view showing aconnection between the corrugated connector plate and the electrodeplate group in a variation of the seventh embodiment;

FIG. 17 is a perspective view showing a connection process of thecorrugated connector plate and the electrode plate group in accordancewith an eighth embodiment of the prismatic battery module of theinvention;

FIG. 18 is a perspective view showing a connection process of thecorrugated connector plate and the electrode plate group in a variationof the eighth embodiment;

FIG. 19 is a horizontal cross-sectional view showing a connectionprocess of the corrugated connector plate and the electrode plate groupin accordance with a ninth embodiment of the prismatic battery module ofthe invention;

FIG. 20 is a perspective view showing a connection process of thecorrugated connector plate and the electrode plate group in a variationof the ninth embodiment;

FIG. 21A is a partial horizontal cross-sectional view showing aconnection between a prismatic battery case and the corrugated connectorplate and the electrode plate group in accordance with a tenthembodiment of the prismatic battery module of the invention, FIG. 21B isa vertical cross-sectional front view showing the connection between theprismatic battery case and the corrugated connector plate and theelectrode plate group in accordance with the tenth embodiment;

FIG. 22A is a perspective view showing a connection between a lid of theprismatic battery case and the upper end of the corrugated connectorplate in accordance with an eleventh embodiment of the prismatic batterymodule of the invention, and FIG. 22B is a vertical cross-sectional viewshowing the connection between the lid of the prismatic battery case andthe upper end of the corrugated connector plate in the eleventhembodiment;

FIG. 23A is a vertical cross-sectional side view showing a sealingstructure between the prismatic battery case and edges of the corrugatedconnector plate in accordance with a twelfth embodiment of the prismaticbattery module of the invention, FIG. 23B is a cross-sectional viewtaken along a line XXIIIB-XXIIIB in FIG. 23A, and FIG. 23C is across-sectional view taken along a line XXIIIC-XXIIIC in FIG. 23A;

FIG. 24A is a horizontal cross-sectional view showing a sealingstructure between the prismatic battery case and edges of the corrugatedconnector plate in accordance with a thirteenth embodiment of theprismatic battery module of the invention, in a normal state, and FIG.24B is a horizontal cross-sectional view showing the sealing structurein an expanded state;

FIG. 25 is a perspective view showing the corrugated connector plate ofthe thirteenth embodiment;

FIG. 26A is a horizontal cross-sectional view showing anotherconstruction of the resilient seal portion of the thirteenth embodiment,and FIG. 26B is a horizontal cross-sectional view showing still anotherconstruction of the resilient seal portion of the thirteenth embodiment;

FIG. 27A is a perspective view showing a connection process between theconnector plate and the electrode plate group in accordance with afourteenth embodiment of the prismatic battery module of the invention,and FIG. 27B is a perspective view as viewed in the opposite direction;

FIG. 28 is a vertical front view showing the adjacent region of aseparation wall in accordance with a fifteenth embodiment of theprismatic battery module of the invention;

FIG. 29A is a horizontal cross-sectional view showing lead portions ofthe electrode plate group in the fifteenth embodiment, and FIG. 29B is aperspective view showing the lead portions of the electrode plate groupin accordance with the fifteenth embodiment;

FIG. 30 is a vertical cross-sectional front view showing a variation ofthe fifteenth embodiment;

FIG. 31A is a horizontal cross-sectional view showing a separation wallof the prismatic battery case in accordance with a sixteenth embodimentof the prismatic battery module of the invention, and FIG. 31B is ahorizontal cross-sectional view showing the separation wall connected tothe electrode plate groups;

FIG. 32 is a partial vertical cross-sectional front view of aconventional prismatic battery module;

FIG. 33 is a partially cutaway perspective view showing a cell case ofthe conventional prismatic battery module; and

FIG. 34 is a descriptive view illustrating the electrical communicationpaths in the conventional prismatic battery module.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A first embodiment of a prismatic battery module of the presentinvention will now be described with reference to FIGS. 1 through 5, inwhich elements identical to those of the prior art described withreference to FIGS. 32 and 33 are denoted by the same reference numerals.The following description is primarily directed to the differences fromthe prior art.

Referring first to FIGS. 1 to 3, a prismatic battery module 1 of thefirst embodiment includes a plurality of cells 2, each of which isconstructed as a nickel metal hydride battery. A prismatic battery case3, formed as a flat rectangular parallelepiped, includes a plurality ofprismatic cell cases 4 for the cells 2. Each cell case 4 has short sidesand long sides and is connected to adjacent ones by sharing the shortsides, which serve as a separation wall 5 for forming the prismaticbattery case 3. A lid 6 covers openings at the top of the cell cases 4connected to one another. The lid 6 includes a communication path 14 forbalancing the internal pressure between the individual cell cases 4, asafety vent (not shown) for discharging the pressure when the internalpressure of the individual cell case 4 exceeds a predetermined value anda sensor fixing hole for fixing a temperature sensor thereto to detectthe temperature of the cell 2.

Each separation wall 5 between the cell cases 4 includes a planarconnector plate 16, which forms at least a part of, and in theembodiment shown, substantially entire part of, the separation wall 5,except the outermost areas thereof. The planar connector plate 16 isintegrally formed with the prismatic battery case 3 by insert molding.As shown in FIG. 2, a connector plate 17, which is an equivalent of theconnector plate 16, is arranged on the inside of the outermost shortside of the connected cell cases 4 on either end of the prismaticbattery case 3. A positive or negative connection terminal 12 extendsfrom the central portion of the connector plate 17, through the shortside wall of the cell case 4, and out of the prismatic battery case 3.

Each cell case 4 accommodates an electrode plate group 8 with anelectrolyte to form the cell 2. The electrode plate group 8 is formed bystacking positive and negative rectangular electrode plates withintervening separators. The positive electrode plates and the negativeelectrode plates have extensions on opposite sides of the electrodeplate group 8 to form positive lead portions 9 a and negative leadportions 9 b, respectively. The lead portions 9 a and the lead portions9 b of adjacent cells are connected to one another by the connectorplates 16 or 17 on both sides of the cell case 4. The lead portions 9 aand the lead portions 9 b are connected to the corresponding connectorplate 16 or 17 by using an electrolyte-resistant, electroconductiveadhesive, or by employing resilient lead portions 9 a and 9 b andpressing them against the connector plate 16 or 17. A plurality ofspaced-apart support holes are provided in the lead portions 9 a and 9 band are denoted by a reference numeral 18. With a positioning pin passedthrough each support hole 18, the side edges of the lead portions 9 a(and 9 b) are pressed against one another, so that the side edges of thelead portions 9 a (and 9 b) are aligned with each other and thus areuniformly held in contact with the connector plate 16 or 17. In thismanner, the plurality of cells 2 accommodated in the prismatic batterycase 3 are connected in series through the planar connector plates 16 ofthe separation walls 5.

The electrode plate group 8 is formed by alternately stacking positiveelectrode plates and negative electrode plates with each positiveelectrode plate covered with a bag-like separator having a side opening.In this manner, the electrode plate group 8 is provided as a stack ofthe positive electrode plates and the negative electrode plates withintervening separators. The positive electrode plate is formed of a Nifoamed metal, which is filled with nickel hydroxide except the part thatcorresponds to the lead portion 9 a. The lead portion 9 a is formed bycompressing the foamed metal and then seam-welding a lead plate onto onesurface of the compressed metal using ultrasound. The negative electrodeplate is formed by applying a paste containing a hydrogen-occludingalloy onto a Ni punched metal, except the part that corresponds to thelead portion 9 b.

An electrolyte is placed in each cell case 4 and the openings of thecell cases 4 are closed with the lid 6. This completes the prismaticbattery module 1.

In the prismatic battery module 1 having the above-describedconstruction, the side edges of the positive lead portions 9 a of theelectrode plate group 8 in one of the cell cases 4 are directlyconnected with the side edges of the negative lead portions 9 b ofanother electrode plate group 8 in the adjacent cell case 4, with theside edges of the lead portions 9 a and 9 b kept in contact with theplanar connector plate 16 in their entire lengths. Since the leadportions 9 a over their entire lengths are held in connection with thelead portions 9 b only through the planar connector plate 16, thecurrent flows through the straight paths between the adjacent electrodeplate groups 8 in the adjacent cells 2, as indicated by the arrows inFIG. 4. Accordingly, the required number of the connection points isreduced and significantly short paths are provided for the current flow.This not only leads to a substantial decrease in the internal resistancebut leads also to a more direct and simpler connection, which enables asignificant cost reduction. Furthermore, unlike the prior art, theprismatic battery module 1 according to this embodiment does not requirethe collector plate, which may lead to a reduction in the cost and helpdecrease the volume of the cell case.

While the example shown in FIGS. 1 through 4 employs the planarconnector plate 16 with a uniform thickness, the connector plate 16 mayhave a thickness that increases in the vertical direction from thethickness t1 at the top of the cell case 4 to the thickness t2 at thebottom of the cell case 4, given that t1<t2. In this manner, the leadportions 9 a and 9 b are brought into firm contact with the connectorplate 16 or 17 to provide reliable connection by simply inserting theelectrode plate group 8 into the cell case 4 from above.

Second Embodiment

Next, a second embodiment of the prismatic battery module of theinvention is described with reference to FIGS. 6A and 6B. In thefollowing description, elements identical to those described inreference to the previous embodiment are denoted by the same referencenumerals and the description thereof will not be repeated. Theembodiment, therefore, is described only in terms of the differences.

In this embodiment, a support pin 19 is placed through each of thesupport holes 18 formed in the lead portions 9 a and 9 b of the positiveand the negative electrode plates of the electrode plate group 8. Also,vertical slots 20 are formed on the opposite side walls of the cell case4 at positions opposite to one another on either side of the separationwall 5, which is arranged between the adjacent cell cases 4 of theprismatic battery case 3, so that the vertical slots 20 opposite to oneanother receive respective ends of the support pin 19 while ends of thelead portions 9 a and 9 b are being resiliently pressed against theplanar connector plate 16.

In this manner, the force resulting from the resilient contact betweenthe lead portions 9 a and 9 b and the planar connector plate 16 is borneby the vertical slots 20 in the prismatic battery case 3 via the supportpin 19. This ensures the firm contact of the lead portions 9 a and 9 bwith the planar connector plate 16. In addition, this constructionallows the components to be connected with small resistance and highreliability.

In this embodiment, the planar connector plate 16 is formed to have anenlarged portion 16 a on either end that is anchored within the sidewall of the prismatic battery case 3. This construction ensures theintegrity as well as the liquid-tightness of the prismatic battery case3 when the connector plate 16 is insert-molded with the prismaticbattery case 3. The construction also ensures that the components areheld together against the expansion of the cell case 4. Preferably, acoating layer 16 b is disposed on the outer surface of the enlargedportion 16 a to improve the sealing performance between the prismaticbattery case 3, which is formed of a resin material, and the planarconnector plate 16, which is formed of a metal material.

Third Embodiment

Next, a third embodiment of the prismatic battery module of theinvention is described with reference to FIGS. 7A and 7B.

In this embodiment, the planar connector plate 16 is welded to the leadportions 9 a and 9 b by applying a welding current that flows through apath between the adjacent support pins 19, which have been described inthe second embodiment above and are arranged on both sides of the planarconnector plate 16. The welding current flows through the support pin19, the lead portions 9 a, the planar connector plate 16, the leadportions 9 b, and the support pin 19 adjacent to the first one to weldthe contacts between the planar connector plate 16 and the lead portions9 a and 9 b.

For this purpose, a pair of work openings 21 are preferably provided onthe respective side walls of the prismatic battery case 3 for providingthe welding current: one of the work openings 21 is formed on one of theopposite side walls at a position adjacent to one end of the support pin19, which is arranged on one side with respect to the planar connectorplate 16, while the other of the work openings 21 is formed on the otherside wall at a position adjacent to one end of the adjacent support pin19, which is arranged on the other side with respect to the planarconnector plate 16. The electrode plate group 8 is placed in each cellcase 4 of the prismatic battery case 3 with its associated support pins19 received in the respective vertical slots 20. In this state, one endof the support pin 19 that is arranged on one side with respect to theplanar connector plate 16 and the opposite end of the adjacent supportpin 19 that is arranged on the other side with respect to the planarconnector plate 16 are exposed in the respective work openings 21. Apair of welding electrodes (not shown) are then connected to therespective ends of the support pins 19 on both sides of the connectorplate 16 to allow the welding current 22 to flow in the directionindicated by the arrows. In this manner, the planar connector plate 16is welded to the lead portions 9 a and 9 b without affecting theelectrode plates of the electrode plate group 8. After welding has beencompleted, the work openings 21 are sealed with resin.

In this embodiment, resistance is further reduced and more reliableconnection is provided since the planar connector plate 16 is welded tothe lead portions 9 a and 9 b. It should be appreciated, however, thatwelding techniques other than the above-described resistance welding mayalso be used. For example, a solder may be applied to the engagingportions of the planar connector plate 16 and the lead portions 9 a and9 b and is then melted by resistance heat to solder the components.

Fourth Embodiment

Next, a fourth embodiment of the prismatic battery module of theinvention is described with reference to FIGS. 8A and 8B.

As shown in FIG. 8A, this embodiment uses a corrugated connector plate23 to serve as an electroconductive connector. The corrugated connectorplate 23 is connected to the lead portions 9 a and 9 b by inserting thelead portions 9 a and 9 b of the positive and the negative electrodeplates of the electrode plate group 8 into respective troughs 23 a and23 b of the corrugated connector plate 23 and then compressing thecorrugation. As a result, the adjacent electrode plate groups 8 areconnected to one another through the corrugated connector plate 23. Arow of the cell cases 4 each housing an electrode plate group 8 isconstructed by connecting a desired number of the electrode plate groups8 with each other through the corrugated connector plates 23, insertingthe connected electrode plate groups 8 into the prismatic battery case 3and joining both ends of each corrugated connector plate 23 to the sidewalls of the prismatic battery case 3 in a liquid-tight manner.

In this regard, a connection bent 24 is formed on either end of thecorrugated connector plate 23, and a slot 25 for receiving theconnection bent 24 is formed at a position corresponding to theseparation wall 5 between the cell cases 4 in the prismatic battery case3. The slot 25 is filled with a sealing material 26 such as pitch tocomplete the cell case 4. In an alternative construction, a T-shapedconnection part 27, made of resin, is arranged on either end of thecorrugated connector plate 23. A T-shaped slot 28 is formed at aposition corresponding to the separation wall 5 between the cell cases 4in the prismatic battery case 3. The connection part 27 is coated with asealing material and is then placed in the T-shaped slot 28.

This embodiment, in which the lead portions 9 a and 9 b are insertedinto the respective troughs 23 a and 23 b of the corrugated connectorplate 23 and are secured by compressing the corrugation, is advantageousin that a large area of contact is achieved, thereby ensuring reliableconnection and a reduced resistance. According to this embodiment, theprismatic battery module is manufactured in an efficient manner by firstconnecting a plurality of the electrode plate groups 8 with each otherthrough the corrugated connector plate 23, inserting the electrode plategroups 8 connected through the corrugated connector plates 23 into theprismatic battery case 3 and then sealing edges of each corrugatedconnector plates 23.

Although the prismatic battery module may be manufactured by firstplacing the corrugated connector plates 23 in the prismatic battery case3 to form the cell cases 4, then inserting the lead portions 9 a and 9 bof the electrode plate groups 8 into the respective troughs 23 a and 23b, and then compressing the corrugation within the cell case 4, theabove-described embodiment provides a more viable and efficient method.

Fifth Embodiment

Next, a fifth embodiment of the prismatic battery module of theinvention is described with reference to FIGS. 9 to 12.

As shown in FIG. 9, this embodiment employs a corrugated connector plate29 having resilience to serve as an electroconductive connector. Thelead portions 9 a and 9 b of the electrode plates are inserted intorespective troughs 29 a and 29 b of the corrugated connector plate 29 sothat the corrugated connector plate 29 resiliently holds the leadportions 9 a and 9 b of the respective electrode plates of the electrodeplate group 8 between its folds. In the example shown in FIG. 9, each ofthe troughs 29 a and 29 b has a pouch-like shape with a space definedtherein and with its opening resiliently closed from both sides to holdthe lead portions 9 a and 9 b.

This embodiment achieves a larger contact area between the corrugatedconnector plate 29 and the lead portions 9 a and 9 b as compared to thecase wherein the lead portions 9 a and 9 b are simply in contact withthe connector plate. Consequently, resistance is reduced and reliableconnection is achieved according to this embodiment. Further, thisembodiment facilitates the connection process since the connectionbetween the components is achieved by simply inserting the lead portions9 a and 9 b into the respective troughs 29 a and 29 b of the corrugatedconnector plate 29.

Referring to FIG. 10, a first variation of this embodiment uses acorrugated connector plate 30 having resilience. The corrugatedconnector plate 30 includes V-shaped troughs 30 a and 30 b with thewidths thereof narrowing toward the bottom of the trough. The leadportions 9 a and 9 b are held in the narrow bottom regions of thetroughs.

Referring to FIG. 11, a second variation uses a corrugated connectorplate 51 having resilience. The corrugated connector plate 51 includespouch-like troughs 51 a and 51 b with lozenge-shaped spaces definedtherein and with their openings resiliently closed from both sides tohold the lead portions 9 a and 9 b. A seal rubber 52 is fixedly baked toeither side edge of the corrugated connector plate 51, and a seal slot53 for receiving the seal rubber 52 is formed on the inner surface ofeach side wall of the prismatic battery case 3 at a position to installthe corrugated connector plate 51.

In a third variation as shown in FIG. 12, the resilient corrugatedconnector plate 51 includes on either side edge thereof apressure-receiving portion 54, which is pressed against the innersurface of each side wall of the prismatic battery case 3. Pressure isapplied to the prismatic battery case 3 from outside and is transmittedthrough the side wall to the pressure-receiving portion 54 to keep thelead portions 9 a and 9 b held by the corrugated connector plate 51. Theseal rubber 52, fixedly baked to the outer surface of the edge of thepressure-receiving portion 54, engages with the seal slot 53 formed oneach side wall to provide sealing. This variation ensures that thecorrugated connector plate 51 is held in contact with the lead portions9 a and 9 b with a substantial pressure through application ofrestrictive force to the prismatic battery case 3 from outside.Consequently, a further reduction in resistance is achieved.

Sixth Embodiment

Next, a sixth embodiment of the prismatic battery module of theinvention is described with reference to FIGS. 13 and 14.

As shown in FIG. 13, this embodiment employs a corrugated connectorplate 55 to serve as an electroconductive connector. The corrugatedconnector plate 55 is connected to the lead portions 9 a and 9 b byinserting the lead portions 9 a and 9 b of the positive and the negativeelectrode plates of the electrode plate group 8 into respective troughs55 a and 55 b and then applying pressure to form a bent 56 in thecorrugation. The seal rubber 52 is fixedly baked to either side edge ofthe corrugated connector plate 55, and the seal slot 53 for receivingthe seal rubber 52 is formed in the inner surface of each side wall ofthe prismatic battery case 3 at a position to install the corrugatedconnector plate 55.

The embodiment, in which the corrugation of the corrugated connectorplate 55 includes the bent 56, is advantageous not only in that thecorrugated connector plate 55 is made more rigid in the direction inwhich the trough 55 a and 55 b open but also in that the contact areabetween the lead portions 9 a or 9 b and the connector plate 55 isincreased by applying a relatively small pressure so as to reduce theresistance.

Referring to FIG. 14, a variation of this embodiment is shown in whichthe corrugation is pressed to form a ridge 57 for the connection of thecorrugated connector plate 55 with the lead portions 9 a and 9 b. Theridge 57 serves to provide the same effects due to its shape and servesto reduce the resistance.

Seventh Embodiment

Next, a seventh embodiment of the prismatic battery module of theinvention is described with reference to FIGS. 15A through 15C and 16.

In this embodiment, a coarse plating 58 having a surface roughness ofabout 5 μm is applied to the surfaces of either or both of the troughs23 a, 23 b and the lead portions 9 a, 9 b in the connection between theelectrode plate group 8 and the corrugated connector plate 23 as shownin FIG. 15B. By compressing the corrugated connector plate 23 with thelead portions 9 a and 9 b positioned in the troughs 23 a and 23 b,respectively, the surfaces having the coarse plating 58 are brought intocontact with each other to form an adhesion layer 59, as can be seen inFIGS. 15A through 15C. In this manner, joints with a large contact areaare formed and a further reduction in resistance is achieved. In thisembodiment, it is preferred that the coarse plating 58 be Ni-basedplating in order to prevent corrosion caused by an electrolyte.

Referring to FIG. 16, a variation of the above-described embodiment usesan electroconductive soft material 60 between the surfaces of troughs 23a and 23 b of the corrugated connector plate 23 and the respective leadportions 9 a and 9 b of the electrode plates. The similarresistance-reducing effects are obtained with this construction. Itshould be appreciated that the electroconductive soft material 60 may beprovided in a continuous form as indicated by the phantom line in thedrawing.

Eighth Embodiment

Next, an eighth embodiment of the prismatic battery module of theinvention is described with reference to FIGS. 17 and 18.

In this embodiment, an electron beam or laser light is irradiated toform a joint between the corrugated connector plate 23 and the leadportions 9 a and 9 b of the electrode plates of the electrode plategroup 8 that are positioned in the respective troughs 23 a and 23 b ofthe connector plate 23, both at the top end and at the bottom end of theconnector plate, thereby welding the lead portions 9 a and 9 b to thecorrugated connector plate 23. In the construction shown in FIG. 17, thebeam is shone vertically and scans along the welding lines 61, that is,along the width of the corrugated connector plate 23, both at the topand at the bottom of the corrugated connector plate 23, whereas, in theconstruction shown in FIG. 18, the beam is shone horizontally from bothsides of the connector plate 23, that is, along the directions leadingfrom the electrode plate groups 8 toward the connector plate 23, andscans along the welding lines 62 a and 62 b, that is, along the width ofthe corrugated connector plate 23, to connect ends of the corrugatedconnector plate 23 with respective ends of the lead portions 9 a and 9 bof the electrode plates.

This embodiment achieves stable connection as well as a reducedresistance since the ends of the lead portions 9 a and 9 b are welded tothe corrugated connector plate 23. Also, the number of steps involved inthe connecting process is reduced by providing welding in the verticaldirection at the both ends of the corrugated connector plate 23 asdescribed in reference with FIG. 17, since the number of welds can be assmall as two in this manner. Although the number of the welds can begreater, the corrugated connector plate 23 is properly welded to thelead portions 9 a and 9 b even when there is a difference in heightbetween the corrugated connector plate 23 and the lead portions 9 a and9 b by welding the ends of the corrugated connector plate 23 to therespective ends of the lead portions 9 a and 9 b of the electrode platesfrom both sides, that is, along the directions leading from theelectrode plate groups 8 toward the connector plate 23, as described inreference to FIG. 18.

Ninth Embodiment

Next, a ninth embodiment of the prismatic battery module of theinvention is described with reference to FIGS. 19 and 20.

Referring first to FIG. 19, an electron beam or laser light isirradiated onto the corrugated connector plate 23 in the direction alongwhich the plates are stacked in the electrode plate group 8, penetratinginto the connector plate 23. As a result, a through weld 64 is formed,which connects the corrugated connector plate 23 with the lead portions9 a and 9 b of the electrode plates. The through weld 64 is formed inline or spots spaced apart from one another along the longitudinaldirection of the corrugated connector plate 23. By allowing the throughwelds 64 to penetrate into the corrugated connector plate 23 from bothsides to a depth greater than half the width of the corrugated connectorplate 23, the lead portions 9 a and 9 b of each electrode plate areconnected to the corrugated connector plate 23.

This embodiment, in which the lead portions 9 a and 9 b are connected tothe corrugated connector plate 23 in their intermediate regions, isadvantageous in that the welds provide a stable connection, forming ashort electrical communication path, which enables further reduction ofresistance.

Referring to FIG. 20, a variation of the above-described embodiment isshown which utilizes the through welds 64 with the penetration depthless than half the width of the corrugated connector plate 23. The leadportions 9 a and 9 b are welded to the corrugated connector plate 23 atlongitudinally spaced-apart positions. The welds are provided inseparate weld groups 66 a and 66 b, so that the welds in the weld group66 a are formed in welding ranges 65 a and the welds in the weld group66 b are formed in welding ranges 65 b, which have different positionsfrom the welding ranges 65 a in the direction along which the electrodeplates are stacked in the electrode plate group 8. A series of cutouts67 are formed on both the corrugated connector plate 23 and eachelectrode plate 68 so that, in each of the weld groups 66 a and 66 b,the electron beam or laser light proceeds without being interruptedoutside the welding ranges 65 a and 65 b. In the example shown, the sameelectrode plates 68 are used but are inverted for those arranged in thewelding range 65 a and for those arranged in the welding range 65 b.

In this manner, proper welding is accomplished to achieve theabove-described advantages, even in cases where the irradiation of theelectron beam or laser light from both sides is not sufficient toprovide enough penetration to reach the center of the corrugatedconnector plate 23 in the direction along which the electrode plates arestacked, to ensure stable welding.

Tenth Embodiment

Next, a tenth embodiment of the prismatic battery module of theinvention is described with reference to FIGS. 21A and 21B.

In this embodiment, a plurality of the electrode plate groups 8 areconnected to one another via the corrugated connector plates 23 to forma connected body, which is then placed in the prismatic battery case 3.A seal rubber 68 is fixedly baked to either side edge of the corrugatedconnector plate 23 and is fitted, while compressed, in a slot 69 formedon the side walls of the prismatic battery case 3 to provide a sealbetween the adjacent cell cases 4. The bottom edge of the corrugatedconnector plate 23 is placed in a slot 70 formed in the bottom innersurface of the prismatic battery case 3 and is embedded in a pitch 71that fills the slot as a sealing material in order to provide sealing.The same sealing structure is provided between the top edge of thecorrugated connector plate 23 and the lid 6. Instead of using the sealrubber 68, sealing may be provided at the side edges of the corrugatedconnector plate 23 by the pitch 71 placed in the slot 69.

This embodiment assures the efficient production of the prismaticbattery module since sealing is provided between the edges of thecorrugated connector plate 23 and the inner walls of the prismaticbattery case 3 by simply inserting the connected body, composed of theelectrode plate groups 8 and the corrugated connector plate 23 connectedto one another, into the prismatic battery case 3.

Eleventh Embodiment

Next, an eleventh embodiment of the prismatic battery module of theinvention is described with reference to FIGS. 22A and 22B.

Referring to FIG. 22A, a vertical sealing wall 72 is formed in the lid 6at a position opposite to the corrugated connector plate 23. The lid 6is placed on top of the prismatic battery case 3 to cover the upperopening thereof. When the prismatic battery case 3 is joined to the lid6, the lower end of the sealing wall 72 is heat-melted by a heat plateand is pressed against the upper end of the corrugated connector plate23 until a flash 73 forms. In this manner, sealing is provided betweenthe prismatic battery case 3 and the lid 6. In order to provide reliablesealing, the flash 73 is properly formed by constructing the portion ofthe sealing wall 72 to be melted larger as compared to the remainder ofthe lid 6.

As in the case of the tenth embodiment, the bottom edge of thecorrugated connector plate 23 is placed in a slot 70, which is formed inthe bottom inner surface of the prismatic battery case 3 and is filledwith the pitch 71 as a seal material, to provide seal.

In this embodiment, seal is provided along a seal line 74, shown as thebroken line in FIG. 22A that extends along the upper edge of thecorrugated connector plate 23. This assures the efficient production ofthe prismatic battery module and makes it possible to establish sealwithout fixedly baking the seal rubber to the top end of the corrugatedconnector plate 23 in a liquid-tight manner. When the seal rubber isfixedly baked, its margin of compression depends upon the margin of theattachment between the prismatic battery case 3 and the lid 6. For thisreason, it is difficult to control the margin of compression in suchcases, which makes it difficult to obtain stable sealing. Thisembodiment is also effective in alleviating this problem.

When pressure builds up in the cell case, the lid 6 tends to deformdownward as the side walls of the cell case expand outward. The sealingwall 72 of the lid 6 of the present embodiment and the resilientcorrugated connector plate 23 effectively cooperate to substantiallyprevent the deformation of the cell case.

Twelfth Embodiment

Next, a twelfth embodiment of the prismatic battery module of theinvention is described with reference to FIGS. 23A through 23C.

In this embodiment, a seal rubber 75 is fixedly baked over the entireperiphery of the corrugated connector plate 23. The periphery of theseal rubber 75 is pressed against the inner walls of the prismaticbattery case 3 and the lid 6 to provide sealing between the adjacentcell cases 4. As can be seen in FIG. 23B, the corrugated connector plate23 is compressed to bring each corrugation into contact with each otherboth at the top end and at the bottom end thereof that are outside theregion of the corrugated connector plate 23 that has the lead portions 9a and 9 b inserted thereinto. The seal rubber 75 is fixedly baked tocover the compressed portions 76.

This embodiment is advantageous in that the resilience of the sealrubber 75 provides a sufficient sealing pressure, thereby simplifyingthe insertion/assembly process of the corrugated connector plate 23 intothe prismatic battery case 3. The construction, in which the top and thebottom ends of the corrugated connector plate 23 are compressed and theseal rubber 75 is fixedly baked to cover the compressed portions,achieves improved sealing performance, which in turn improves theworkability.

While in this embodiment, the seal rubber 75 is fixedly baked over theentire periphery of the corrugated connector plate 23, only part of theperiphery may be sealed by using other sealing materials such as pitch.

Thirteenth Embodiment

Next, a thirteenth embodiment of the prismatic battery module of theinvention is described with reference to FIGS. 24A through 26B.

Referring to FIGS. 24A and 24B, a resilient seal portion 77 is formed oneither side of the corrugated connector plate 23. As shown in FIG. 25,the resilient seal portion 77, which has a resilience and tends toexpand outward, has a width that has the largest value at its center inthe vertical direction and gradually decreases toward the top and thebottom ends thereof.

As indicated by the phantom line in FIG. 24A, the side wall of theprismatic battery case 3 can be displaced outward by as much as adistance d (2 to 3 mm at most) as the electrode plate group 8 expands orcontracts upon charging/discharging of the battery. When this happens,the resilient seal portion 77 follows the side wall and remains incontact with the prismatic battery case 3. Accordingly, the seal betweenthe cell cases 4 is maintained. When the prismatic battery case 3expands, the side walls expands most at the central region thereof inthe vertical direction, which is the most distant region from the bottomwall and the lid of the prismatic battery case 3 that providesconfinement for the side walls. Since the resilient seal portion 77 hasa width that has the largest value at its center in the verticaldirection and gradually decreases toward the top and the bottom endsthereof, it expands most at the center to follow the shape of theexpanded prismatic battery case 3. Consequently, the resilient sealportion 77 effectively provides sealing between the cell cases 4 overthe vertical length thereof.

As shown in FIGS. 26A and 26B, the resilient seal portion 77 may beconfigured to have a cross-section with its width decreasing toward theedge thereof. In this manner, the ability of the resilient seal portion77 to follow the side wall, as well as its sealing performance, isimproved. The resilient seal portion 77 may include a rubber piece 78fixedly baked to the corrugated connector plate 23 at either side edgethereof, as shown in FIG. 26A. Alternatively, it may include a metalplate 79, which may be integrally formed with the corrugated connectorplate 23 or may be secured to the corrugated connector plate 23 oneither edge, and a rubber 80 fixedly baked to the edge of the metalplate 79, as shown in FIG. 26B.

Fourteenth Embodiment

Next, a fourteenth embodiment of the prismatic battery module of theinvention is described with reference to FIGS. 27A and 27B.

Referring to FIGS. 27A and 27B, the lead portions 9 a and 9 b of theelectrode plates of the electrode plate group 8 are welded to a planarconnector plate 81 on either side thereof. The planar connector plate 81is not integrally formed with the prismatic battery case 3 by insertmolding. In particular, one or more of cutouts 82 are formed on theelectrode plates of the adjacent electrode plate groups 8 on the sidesfacing the planar connector plate 81. The intersecting points betweenboth ends of the lead portions 9 a and 9 b and the planar connectorplate 81, as well as between each corner of the cutout 82 and the planarconnector plate 81, are fillet-welded to form welds 83, which connectthe electrode plate group 8 with the planar connector plate 81. Asealing material 84 such as a fixedly baked rubber or other material isarranged over the periphery of the planar connector plate 81 to providesealing between the connector plate 81 and the inner surface of theprismatic battery case 3 and thus seal the cell cases 4 from oneanother.

Using the separate planar electroconductive connector from the prismaticbattery case 3, this embodiment facilitates manufacture of the prismaticbattery module and thus reduces the production cost. It also helpsreduce the resistance of the connection since the lead portions 9 a and9 b of the electrode plates of the electrode plate group 8 are connectedto the planar connector plate 81 through three, four, or more of thewelds 83.

Fifteenth Embodiment

Next, a fifteenth embodiment of the prismatic battery module of theinvention is described with reference to FIGS. 28 to 30.

Referring to FIG. 28, a block electroconductive connector 31 isintegrally formed with the separation wall 5, which is arranged betweenthe cell cases 4 of the prismatic battery case 3, at the substantiallycentral portion of the separation wall 5 by insert molding. Theelectroconductive connector 31 includes a raised portion that projectsinto the cell case 4 on either side and has a tapered connection surface32, which comes close to the other connection surface 32 in a taperedfashion as it extends upward. As shown in FIGS. 29A and 29B, a raisedportion 33 is formed in the lead portions 9 a and 9 b of the electrodeplate group 8 at the central portion thereof. The raised portion 33corresponds to the raised portion of the electroconductive connector 31and includes a sloped surface 34 that comes in surface contact with thetapered connection surface 32. With electroconductive spacers 35interposed between them, the lead portions 9 a and 9 b of the electrodeplate group 8 are welded together by, for example, beam weld 36, so thatthey together form a block.

The electrode plate group 8 is placed in each cell case 4 of theprismatic battery case 3 so that the sloped surfaces 34 of the raisedportion 33 of the lead portions 9 a and 9 b come into surface contactwith the respective tapered connection surfaces 32 of theelectroconductive connector 31 projecting from the separation wall 5. Alaser beam is irradiated through the upper opening of the cell case 4and a work opening 37 formed on the bottom of the cell case 4 onto theupper and the lower sides of the contact surface between the taperedconnection surface 32 and the sloped surface 34 to form a laser beamweld 38. As a result, the row of the electrode plate groups 8 in therespective cell cases 4 are interconnected in series via theelectroconductive connectors 31. After welding has been completed, thework opening 37 is closed by plugging a resin plate 39 thereinto andheat-melting the resin plate. An electrolyte is then poured into thecell cases 4.

This embodiment, in which the raised portions 33 of the lead portions 9a and 9 b of the electrode plate group 8 are welded to theelectroconductive connector 31 integrally formed with the separationwall 5, provides reliable connection between the electrode plates of theelectrode plate group 8 and the electroconductive connector 31.Furthermore, the connection between the electroconductive connector 31and the lead portions 9 a and 9 b is made even more reliable and theresistance of the connection is further reduced since theelectroconductive connector 31 includes the tapered connection surfaces32, which is exposed within the cell case 4, and the raised portion 33of the lead portions 9 a and 9 b includes the sloped surface 34 to comeinto contact with the tapered connection surfaces 32.

Aside from the above-described tapered connection surface 32, theconnection surface of the electroconductive connector 31 to be exposedwithin the cell case 4 may be configured as shown in FIG. 30: aconnection surface 40 facing upward is provided to come into surfacecontact with the lower surface of the raised portion 33 of the leadportions 9 a and 9 b. Rather than using laser beam irradiation, thecontact surface is welded by forming a resistance weld 41 by pressingthe surfaces against one another as indicated by the arrows and applyingthe welding current.

Sixteenth Embodiment

Next, a sixteenth embodiment of the prismatic battery module of theinvention is described with reference to FIGS. 31A and 31B.

Referring to FIGS. 31A and 31B, a crank-shaped connector plate 42includes a connection surface 43 at the middle portion thereof along thewidth of the cell case. The connection surface 43 extends in thedirection of the arrangement of the cell cases 4. The lead portions 9 aand the lead portions 9 b of the respective electrode plates 8 that areto be connected are extended in order to be placed on both sides of theconnection surface 43 so that the stack of the lead portions 9 a and thestack of the lead portions 9 b are positioned side by side. The stack ofthe lead portions 9 a and the stack of the lead portions 9 b of eachelectrode plate group 8 are pressed against one another from above thebattery case as indicated by the arrows, with the connection surface 43interposed between them. The welding current is then applied to connectthe stacks of the lead portions 9 a and 9 b of the respective electrodeplate groups 8 with each other, with the connection surface 43interposed between them.

This embodiment achieves reliable connection with reduced resistancesince the lead portions 9 a and 9 b each include an extension to allowthe stacks of the lead portions 9 a and 9 b to be welded to one another,with the connection surface 43 of the crank-shaped connector plate 42interposed between them.

The prismatic battery module of the present invention, as well as itsmanufacturing method, is advantageous in that it reduces the heatgeneration of the battery and realize a high power battery with longerlife and in that the resistance of the components is minimized to reducethe internal resistance of individual cells. Not requiring collectorplates, the prismatic battery module of the present invention is alsoadvantageous in that it reduces the manufacturing cost and achieve acell case with a smaller volume. The present invention is particularlyadvantageous when applied to battery modules using battery cases made ofsynthetic resin, exhibiting a relatively low cooling performance.

Although the present invention has been fully described in connectionwith the preferred embodiment thereof, it is to be noted that variouschanges and modifications apparent to those skilled in the art are to beunderstood as included within the scope of the present invention asdefined by the appended claims unless they depart therefrom.

1. A prismatic battery module comprising: a prismatic battery casehaving a plurality of prismatic cell cases connected to one anotherthrough separation walls; an electroconductive connector forming atleast a central part of the separation wall arranged between the cellcases; an electrode plate group arranged in each of the plurality ofcell cases, the electrode plate group including positive electrodeplates, negative electrode plates, and separators interposedtherebetween, and further forming lead portions by projecting one sideportion of the positive electrode plates and one side portion of thenegative electrode plates in opposite directions, respectively; and anelectrolyte accommodated in each of the cell cases, wherein the positiveelectrode plates and the negative electrode plates are directlyconnected to the respective electroconductive connectors arranged onboth sides of each cell case.
 2. The prismatic battery module accordingto claim 1, wherein the electroconductive connector comprises a planarconnector plate being integrally formed with the prismatic battery case,and the lead portion of each of the electrode plates is connected to theconnector plate.
 3. The prismatic battery module according to claim 2,wherein the connector plate has a thickness increasing from top tobottom of the cell case.
 4. The prismatic battery module according toclaim 2, further comprising a support pin arranged on either side of theelectrode plate group through the lead portions of the electrode plates,and a vertical slot formed in either side wall of the cell case toreceive each end of the support pin, wherein ends of the lead portionsare resiliently pressed against the connector plate, and a force exertedby the lead portions is borne by the vertical slot via the support pin.5. The prismatic battery module according to claim 4, wherein the leadportions are welded to the connector plate by applying a welding currentbetween the support pins arranged on both sides of the connector plate.6. The prismatic battery module according to claim 1, wherein theelectroconductive connector comprises a crank-shaped connector plateincluding a connection surface in a middle portion thereof, theconnection surface extending in a direction in which the cell cases arearranged in a row, wherein the lead portions of the electrode plates ofthe adjacent electrode plate groups each include an extension to allow astack of the lead portions to be formed and welded to an adjacent stackof the lead portions of the adjacent electrode plate group in such amanner that one of the stacks of the lead portions is stacked on top ofthe other with the connection surface interposed between the stacks ofthe lead portions.
 7. The prismatic battery module according to claim 1,wherein the electroconductive connector comprises a planar connectorplate, and one or more of cutouts are formed in the electrode plates ofthe electrode plate groups adjacent to one another on sides facing theplanar connector plate, and intersecting points between both ends of theside edges of the electrode plates and the connector plate and betweencorners of the cutouts and the connector plate are welded to connect theelectrode plates to the connector plate, wherein a sealing material isarranged over a periphery of the connector plate to provide sealingbetween the connector plate and an inner surface of the prismaticbattery case, thereby sealing the cell cases from one another.
 8. Theprismatic battery module according to claim 1, wherein theelectroconductive connector comprises a corrugated connector plate, andthe lead portions of the electrode plates are inserted into respectivetroughs of corrugation to connect the electrode plates to the corrugatedconnector plate.
 9. The prismatic battery module according to claim 8,wherein the corrugation is compressed following insertion of the leadportions into the respective troughs, to connect the electrode plates tothe corrugated connector plate.
 10. The prismatic battery moduleaccording to claim 8, wherein the lead portions of the electrode platesare connected to the corrugated connector plate by allowing the leadportions and the connector plate to press against each other.
 11. Theprismatic battery module according to claim 10, wherein the leadportions of the electrode plates are held in contact with the corrugatedconnector plate by allowing both ends of the corrugated connector plateto press against the inner wall of the prismatic battery case andutilizing resulting force to keep the corrugated connector plate incontact with the lead portions of the electrode plates.
 12. Theprismatic battery module according to claim 8, wherein the corrugatedconnector plate includes a bent.
 13. The prismatic battery moduleaccording to claim 8, wherein the corrugated connector plate includes aridge.
 14. The prismatic battery module according to claim 8, whereineither or both of the troughs and the lead portions of the electrodeplates includes a coarse plating applied to surfaces thereof.
 15. Theprismatic battery module according to claim 8, wherein anelectroconductive soft material is interposed between surfaces of thetroughs and the respective lead portions of the electrode plates. 16.The prismatic battery module according to claim 8, wherein the leadportions of the electrode plates of the electrode plate group areinserted into the troughs of the corrugated connector plate and arewelded to the corrugated connector plate on top and bottom ends thereof.17. The prismatic battery module according to claim 16, wherein weldingis performed by vertically irradiating an electron beam or laser lightat both ends of the corrugated connector plate.
 18. The prismaticbattery module according to claim 16, wherein an electron beam or laserlight is irradiated horizontally from both sides of the corrugatedconnector plate, along directions leading from the electrode plategroups toward the connector plate, to connect ends of the corrugatedconnector plate with the respective ends of the lead portions of theelectrode plates.
 19. The prismatic battery module according to claim 8,wherein an electron beam or laser light is irradiated onto thecorrugated connector plate in a direction along which the electrodeplates are stacked in the electrode plate group to penetrate into theconnector plate thereby welding the corrugated connector plate to thelead portions of the electrode plates.
 20. The prismatic battery moduleaccording to claim 19, wherein the lead portions are welded to thecorrugated connector plate at longitudinally spaced-apart positions,welds being provided in individual weld groups such that the welds areformed in welding ranges that are different from one weld group toanother, the welding ranges defined in a direction along which theelectrode plates are stacked in the electrode plate group, while aplurality of cutouts are formed both on the corrugated connector plateand on each electrode plate in order to allow the electron beam or laserlight to proceed without being interrupted outside the welding ranges,in each of the weld groups.
 21. The prismatic battery module accordingto claim 8, wherein at least a part of the periphery of the corrugatedconnection plate is placed in a slot formed in a side wall of theprismatic battery case at a position that corresponds to the separationwall arranged between the cell cases, with a sealing material beingapplied thereto to provide sealing.
 22. The prismatic battery moduleaccording to claim 8, wherein a slot is formed on a bottom surface ofthe prismatic battery case to receive one end of the corrugatedconnector plate and is filled with a sealing material, such that the endof the corrugated connector plate is placed in the sealing material inthe slot to provide sealing.
 23. The prismatic battery module accordingto claim 8, wherein a vertical sealing wall is formed in a lid forclosing an upper opening of the prismatic battery case at a positionopposite to the corrugated connector plate and, when the prismaticbattery case is joined to the lid, a lower end of the sealing wall isheat-melted and pressed against an upper end of the corrugated connectorplate to provide sealing.
 24. The prismatic battery module according toclaim 8, wherein a seal rubber is fixedly baked to the corrugatedconnector plate over at least part of its periphery, and the peripheryof the seal rubber is pressed against an inner wall of the prismaticbattery case to seal the cell cases from one another.
 25. The prismaticbattery module according to claim 24, wherein the corrugated connectorplate is compressed to bring each corrugation into contact with eachother at a top end and at a bottom end thereof that are outside a regionof the corrugated connector plate that has the lead portions insertedthereinto, and the seal rubber is fixedly baked to cover the compressedportions.
 26. The prismatic battery module according to claim 8, whereina resilient seal portion is formed on either side of the corrugatedconnector plate, the resilient seal portion having a resilience andtends to expand outward.
 27. The prismatic battery module according toclaim 26, wherein the resilient seal portion has a width that has thelargest value at its center in a vertical direction and graduallydecreases toward top and bottom ends thereof.
 28. The prismatic batterymodule according to claim 26, wherein the resilient seal portion has across-section with its width decreasing toward the edge thereof.
 29. Theprismatic battery module according to claim 26, wherein the resilientseal portion comprises a rubber piece fixedly baked to the corrugatedconnector plate at either side edge thereof.
 30. The prismatic batterymodule according to claim 26, wherein the resilient seal portioncomprises a metal plate, which is integrally formed with the corrugatedconnector plate or secured to the corrugated connector plate on eitheredge, and a rubber fixedly baked to an edge of the metal plate.